Endotoxin-induced oxidative stress in the rat small intestine: role of nitric oxide.

Reactive oxygen species have been implicated in the gastrointestinal pathogenesis of septic and endotoxic shock. The objective of this study was to investigate the role of inducible nitric oxide synthase during endotoxin-induced formation of oxidants by cells of the small intestine. After intravenous Escherichia coli lipopolysaccharide (LPS) (1 mg/kg) injection, nitric oxide production was measured as nitrosyl complex formation in the ileum using electron paramagnetic resonance spectroscopy. Oxidative stress biomarkers were determined as duodenal mucosal-reduced thiols, the ileal lipid peroxidation and luminal free radical production using spin trapping methodology. Demonstration of nitrosyl complex formation commenced at 3 h and diminished 24 h post-LPS. Mucosal thiol levels were decreased at 3, 6, 12, and 18 h post-LPS treatment. At these time point, the ileal lipid peroxidation also increased as did luminal formation of hydroxyl radical adduct. Nitric oxide synthase inhibitors reversed the elevation of hydroxyl radical formation and reversed the decrease in mucosal-reduced thiol levels in the LPS-treated rats. Our data indicate that nitric oxide or its oxidant product(s), such as peroxynitrite, contribute to oxidative injury in the small intestine of rats treated with endotoxin.

Nitrosyl complex formation during endotoxin-induced injury in the rat small intestine.

The objective of this study was to demonstrate nitric oxide (NO) production and determine its role in the rat small intestine following endotoxin treatment. By using electron paramagnetic resonance (EPR) spectroscopy, we were able to detect high concentrations of nitrosylated proteins in the small intestines of rats administered 1 mg/kg lipopolysaccharide (LPS) and sacrificed 6 h later. EPR spectra of non-heme and heme nitrosyl complexes were detected in the epithelium layer and intestinal wall. Only EPR spectra characteristic of nitrosyl hemoprotein complexes were detected in the luminal contents of these rats. LPS administration elevated the concentrations of intestinal lipid peroxidation biomarkers, thiobarbituric acid-reactive substances, and conjugated dienes. These changes were attenuated by NO synthase inhibitor treatment. We conclude that oxidants associated with NO formation were at least in part involved in the oxidation of tissue lipids. This process may be one of the mechanisms of intestinal injury induced by LPS.